This morning I moderated a couple of answers which had spam flags on them. They weren't spam. These particular answers were not answers, and should have been flagged as 'not an answer'. Ergo this post.
What is Spam?
Spam is Unsolicited Commercial Advertisement. You've all seen it. Spam doesn't mean "I don't like the answer" or "this answer is noise."
What is the effect of the Spam flag?
This type of flag receives an extremely high priority in the moderation queue. It should be used only when the content of the post you are flagging meets the criteria defined below, or it will likely be declined.
The spam flag is designed to eliminate posts with no relevant content and to penalize the authors
I highly recommend reading that second link above, as it thoroughly-describes when and why things should be flagged as spam.